The present invention relates to a method for the presulfurization of a hydrogenation catalyst.
The conventional method for presulfurizing hydrogenation catalysts is an in-situ (inside reactor) method of presulfurization, comprising: placing a catalyst having hydrogenation-active metal in oxidation state in a reactor and presulfurizing the catalyst at a high temperature by passing through hydrogen and hydrogen sulfide or hydrogen and a straight fraction oil containing carbon disulfide and dimethyl disulfide to convert the hydrogenation-active metal into sulfurization state. The in-situ method of presulfurization has the disadvantages of higher production costs, prolonged time for presulfurization and flammable and poisonous sulfides being used, thus causing environmental pollution.
Another method for presulfurizing hydrogenation catalysts is ex-situ (outside reactor) method of presulfurization, which means combining a hydrogenation catalyst and a vulcanizing agent prior to loading them into the reactor, then only introducing hydrogen or hydrogen and oils simultaneously to start up the presulfurization, and subsequently raising the temperature, thus completing the sulfurization activation process. Since the ex-situ method of presulfurization has advantages of simple operation, high efficiency and non-pollution, this method is used widely. In this ex-situ method of presulfurization, the vulcanization agent usually used is elemental sulfur and/or organic polysulfides.
In U.S. Pat. No. 4,089,930, a hydrotreating process of hydrocarbon raw materials is disclosed, which comprises contacting the hydrocarbon raw material with hydrogen and a hydrotreating catalyst as an elevated temperature to remove sulfur, nitrogen and oxygen there from, the improvement lies in that a sulfurized catalyst is used in the process, wherein said catalyst is obtained by presulfurizing the catalyst supported with metal oxides in the following steps: contacting the supported catalyst of metal oxides with elemental sulfur in the absence of hydrogen to allow at least a part of said elemental sulfur entering the pores in the catalyst. The sulfur-incorporated catalyst is contacted with hydrogen at 200xcx9c600xc2x0 C. The method has advantages of low cost and high efficiency. However, since it is the nature of elemental sulfur to sublime easily and to be dissolvable in raw material oil, if there is no protective measure, the elemental sulfur in the catalyst will be very easily stripped off upon start-up, and as a result the catalyst can not be completely sulfurized and thus the catalyst will not have sufficient activity, and excessive sulfur will exist in the products. In some case as sulfur is stripped off, elemental sulfur will be condensed in the pipes downstream the apparatus to cause a sudden stop for blocked pipelines in production. Thus, it can be seen that, how to increase the sulfur retention degree in catalyst is a key problem which should be solved before commercial application of the ex-situ method of presulfurization when elemental sulfur is used as a vulcanizing agent.
To solve this problem of sulfur being stripped off, in EP 359,356 A1 two presulfurization methods of hydrotreating catalysts are proposed. One comprises: (1) contacting the catalyst with a powdered elemental sulfur at a temperature lower than 210xc2x0 F. (about 99xc2x0 C.) to allow said elemental sulfur entering essentially the pores in the catalyst to form a mixture; and (2) heating said mixture to a temperature in the range of higher than the melting point of elemental sulfur and below 390xc2x0 F. (about 199xc2x0 C.) in absence of hydrogen. Another one comprises (1) contacting the catalyst with a powdered elemental sulfur at a temperature lower than 210xc2x0 F. (about 99xc2x0 C.) to allow said elemental sulfur entering essentially the pores in the catalyst to form a mixture; and (2) mixing said mixture with at least one substance selected from a hydrocarbon solvent and an oil having a high boiling range to form a prewetted mixture, and the method also comprises further heating said prewetted mixture to a temperature higher than the melting point of sulfur. Using these methods mentioned above, the stripping loss of sulfur is decreased, and thus the retention degree of sulfur is increased.
In U.S. Pat. No. 5,215,954, two presulfurization methods of the catalyst containing metal oxides are disclosed, the first one comprises (1) contacting said catalyst with elemental sulfur by sublimation and/or melting at such a temperature as to allow said elemental sulfur entering essentially the pores in the catalyst, (2) heating the sulfur-incorporated catalyst at a temperature higher than 150xc2x0 C. in the presence of liquid olefin. The second method comprises contacting said catalyst with the mixture of a powdered elemental sulfur and a liquid olefin, and heating the resultant mixture to above 150xc2x0 C. By this method, stripping loss of sulfur is further decreased, and the retention degree of sulfur is increased.
In U.S. Pat. No. 5,681,787, a presulfurization method of hydrogenation catalyst particles containing at least one metal or metal oxide is disclosed, wherein the method comprises (1) contacting said catalyst with elemental sulfur at such a temperature as to allow at least a part of said elemental sulfur entering the pores in the catalyst, (2) contacting said catalyst with at least one of oxygen-containing hydrocarbons having at least 12 carbon atoms to obtain a catalyst having a decreased autothermicity.
Although the retention degree of sulfur is increased to a certain extent by using various methods mentioned above, it is still far from being enough.
CN 85107953A discloses a presulfurization method of catalyst, wherein said catalyst comprises at least one metal or non-metal oxide carrier and at least one active metal, in the first reaction stage, said catalyst is treated with at least one vulcanizing agent at 0-50xc2x0 C. in the absence of hydrogen to allow the vulcanizing agent to permeate partially or completely through the pores in the catalyst, in which said vulcanizing agent is a polysulfide having a general formula as follows: Rxe2x80x94S(n)xe2x80x94Rxe2x80x2, wherein n is a number in the range of 3-20, Rxe2x80x2 represents a hydrogen atom or other group similar or not similar to R group, both said groups represent respectively an organic group having 1-150 carbon atoms and may be one selected from the group consisting of saturated or unsaturated linear, branched or cyclic alkyl group, aryl group, alkylaryl group and arylalkyl group, and the vulcanizing agent is used in the form as it is dissolved in a solvent. Then the catalyst is subjected to drying treatment. Thereafter in the second reaction stage, the treated catalyst from the first reaction stage is further treated in the following procedures: (1) treating the catalyst in the absence of hydrogen but in the presence of an inert or non-inert gas at a temperature of 65-275xc2x0 C. and a pressure of 0.5-70 bar for at least 5 minutes, then (2) treating the catalyst further at a temperature of at least 275xc2x0 C. for at least 1 minute.
U.S. Pat. No. 5,139,990 discloses a preparation method of a catalyst for hydrotreating hydrocarbon raw materials, wherein the method comprises (1) preparing a catalyst which comprises a carrier material onto which one or more active metal or metal compounds for hydrotreating the hydrocarbon raw materials are deposited; (2) contacting the catalyst from the step (1) with a liquid medium containing an organic sulfur compound to introduce an effective amount of the organic sulfur compound into the catalyst, said organic sulfur compound is one selected from the group consisting of a salt of ethylene bis-(dithio carbamic acid), a salt of 2,5-dimetacapto-1,3,4-thiobiazole, thiourea, ammonium thiocyanate, dimethyl sulfoxide, 3,4-dithiaadipate 2,2xe2x80x2-dithioethylene glycol.
In both methods mentioned above, organic compounds of sulfur are used as the vulcanizing agent, but in the ex-situ method of presulfurization, there is a tendency to use elemental sulfur as the vulcanizing agent, because, compared with elemental sulfur, the vulcanizing agent used in both methods mentioned above are very expensive in price, and thus using in a large amount of the expensive organic sulfur compounds results in increasing the cost of the presulfurization method, therefore it is disadvantageous to commercial application.
CN 1082591A discloses a method for treating the catalyst containing at least one of metal or non-metal oxides and at least one of active metals, in said method at least one vulcanizing agent is used for treating the catalyst, said vulcanizing agent is one selected from the group consisting of elemental sulfur and an organic sulfur compound having a general formula of Rxe2x80x94S(n)xe2x80x94Rxe2x80x2, wherein n is a number of 3-20, R and Rxe2x80x2 may represent same, or different groups, each having 1-150 carbon atoms in molecule, selected from the group consisting of saturated or unsaturated, linear or branched alkyl, aryl, alkylaryl and arylalkyl group, Rxe2x80x2 may also represent a hydrogen atom. In said method a mixture solvent is added to dilute the vulcanizing agent and said mixture solvent comprises further at least one component of olefin-containing carbon chain. In the method, the vulcanizing agent used is elemental sulfur, polysulfide or a mixture thereof. If the vulcanizing agent used is solely elemental sulfur, there will be no difference between this method and U.S. Pat. No. 5,215,954 and U.S. Pat. No. 5,681,787. If only polysulfide is used as the vulcanizing agent, still the disadvantage of expensive price is inevitable. However, if a mixture of the two is used as the vulcanizing agent, the sulfur content from the polysulfide is about 5-75 wt %, preferably 20-60 wt %, more preferably 25-50 wt % of the mixture of polysulfide and elemental sulfur, the amount of polysulfide used is still relatively high. Furthermore, when a mixture of the two is used as the vulcanizing agent, the increase in the sulfur retention degree is not enough.
The object of the present invention is to provide a new presulfurization method of hydrogenation catalyst which is able to increase further the sulfur retention degree in the catalyst.
The presulfurization method of hydrogenation catalyst according to the present invention comprises contacting said catalyst with elemental sulfur at a temperature to allow said elemental sulfur substantially incorporated into the pores of the catalyst by the subliming and/or melting process, said method comprises further (1) mixing a olefin-containing component, elemental sulfur and a promoter, and heating the resultant mixture at 100xcx9c220xc2x0 C. for more than 0.5 hour, wherein the mole number of elemental sulfur is not less than the mole number of double bond of the olefin, and the amount of the promoter used is 10-80 wt % of the elemental sulfur used, and said promoter is one or more organic promoters usually used in rubber curing; (2) impregnating the sulfurized olefin-containing product obtained from the step (1) onto the elemental sulfur-incorporated catalyst, and heating the catalyst at 100xcx9c300xc2x0 C. in an inert atmosphere for more than 1 hour, wherein the volume amount of the sulfurized olefin-containing product is at least 60 vol % of pore volume of the catalyst.
According to the method of the present invention, said hydrogenation catalyst is a hydrotreating catalyst (for hydrodesulfurization, hydrodenitrogenation and hydrodearomatization) comprising heat-refractory inorganic oxides (such as alumina, silica, alumina-silica) as a carrier on which one or more oxides of the metals selected from the elements of GVIII or GVIB in the periodic table of elements are supported, or a hydrocracking catalyst comprising zeolites and heat-refractory inorganic oxides as a carrier, on which one or more oxides of metals selected from the elements of GVIII or GVIB in the periodic table of elements are supported. The Preferred hydrogenation catalyst is a hydrotreating catalyst (for hydrodesulfurization, hydrodenitrogenation, hydrodearomatization) comprising heat-refractory inorganic oxides (such as alumina, silica, alumina-silica) as a carrier on which one or two compound(s) selected from nickel and/or cobalt oxides and one or two selected from molybdenum and/or tungsten oxides are supported, or a hydrocracking catalyst comprising zeolite and heat-refractory inorganic oxides as a carrier on which one or two compound(s) selected from nickel and/or cobalt oxides and one or two compound(s) selected from molybdenum and/or tungsten oxides are supported. Said catalysts may further comprise a cocatalyst component such as fluorine, phosphor, boron and the like.
Said step of contacting the catalyst with elemental sulfur by the sublimitation and/or melting process is carried out by conventional method, that is, by heating the mixture of catalyst sample and elemental sulfur to a temperature higher than 80xc2x0 C., preferably 80xcx9c445xc2x0 C., more preferably 90xcx9c130xc2x0 C., then keeping the temperature constant for more than 0.5 hour, preferably 0.5xcx9c5 hours. The amount of elemental sulfur used depends on the amount of metal to be sulfurized in the catalyst. Generally speaking, the amount of elemental sulfur used is 50xcx9c150 wt % of stoichiometric value in presulfurization, preferably 90xcx9c140 wt % of the stoichiometric value. For example, in the case of a catalyst containing 24.5 wt % of tungsten oxide, 2.5 wt % of nickel oxide, the sulfides formed in the sulfurization are WS2 and Ni3Sz, the stoichiometric value is 7.5 g sulfur/100 g catalyst. Thus, the amount of elemental sulfur used is 3.75xcx9c11.25 g sulfur/100 g catalyst, preferably, 6.25xcx9c10.5 g sulfur/100 g catalyst.
Said olefin-containing component may be one or more selected from pure liquid monoene, diene and polyene, and said monoene, diene and polyene may be a linear, branched or cyclic olefin. Said olefin is preferably an olefin having 5xcx9c30 carbon atoms. Said olefin-containing component may contain other hydrocarbon components, such as one or more selected from alkane, cycloalkane and aromatic hydrocarbon, and in said olefin-containing component, olefin content is 30xcx9c100 wt %. In order to reduce the costs, the fraction oil containing olefin can be used as the olefin-containing component, provided that the olefin content is at least 30 wt %, and other main components in the fraction oil are preferably alkane or cycloalkane with low toxicity. In order to reduce further the costs, said olefin-containing component can be selected from the fraction oils having a boiling range of 170xcx9c350xc2x0 C. and an olefin content of 50xcx9c90 wt %, originated from wax cracking.
Said promoter is one or more conventional organic promoters used in rubber curing. These conventional promoters are described in detail in the xe2x80x9cPromoters Handbook in Plastics and Rubbersxe2x80x9d, pp 458-536, Chief-editor Lui Si-guang, China Light Industry Press, 1995. Said promoter is preferably one or more metal-free organic promoters used in rubber curing, in which it is more preferably as follows:
(1). tetramethylthiuram disulfide having the formula: 
(2). tetraethylthiuram disulfide having the formula: 
(3). tetramethylthiuram sulfide having the formula: 
(4). tetramethylthiuram tetrasulfide having the formula: 
(5). 2-mercapto benzothiazole having the formula: 
(6). dibenzothiazole disulfide having the formula: 
(7). N,N-diisopropyl-2-benzothiazole sulfenamide having the formula: 
(8). N-tert-butyl-2-benzothiazole sulfenamide having the formula: 
(9). N,N-dicyclohexyl-2-benzothiazole sulfenamide having the formula: 
(10). N,O-di(1,2-ethylene)-2-benzothiazole sulfenamide having the formula: 
(11). 1,2-ethylene thiourea having the formula: 
(12). N,N-di-n-butyl thiourea having the formula: 
(13). diphenyl thiourea having the formula: 
(14). dithio-di-n-butyl xanthic acid having the formula: 
(15). diphenylguanidine having the formula: 
(16). di-o-tolylguanidine having the formula: 
(17). triphenylguanidine having the formula: 
(18). N,O-di(1,2-ethylene)thiocarbamyl-N,O-di(1,2-ethylene)sulfenamide having the formula: 
According to the method of the present invention, the amount of said promoter used is 10xcx9c80 wt %, preferably 10xcx9c50 wt %, of the amount of elemental sulfur used in the reaction mixture of the olefin-containing component, elemental sulfur and promoter. Since the elemental sulfur contained in the reaction mixture of the olefin-containing component elemental sulfur and promoter makes up only a small part of the amount of elemental sulfur used in the reaction, the amount of sulfur form the promoter accounts for no more than 7 wt %, preferably no more than 4 wt %, of the total amount of sulfur used in the reaction.
Said heating temperature, after the olefin-containing component, elemental sulfur and promoter are mixed is preferably 130xcx9c210xc2x0 C., more preferably 150xcx9c190xc2x0 C., while the heating time is preferably 0.5xcx9c5 hours. The amount of said promoter used is preferably 10xcx9c50 wt % of the amount of elemental sulfur used.
When impregnating the elemental sulfur-incorporated catalyst with the sulfurized olefin-containing product, the amount of the sulfurized olefin containing product used is preferably 60xcx9c150 vol % of the pore volume of the catalyst. In order to maintain the catalyst in a dry state to facilitate the heat treatment in the next step, the amount of the sulfurized olefin-containing product used is preferably 75xcx9c95 vol % of the pore volume of the catalyst.
Said inert atmosphere refers to any atmosphere which does not react with said elemental sulfur and metal, such as Helium, Neon, Argon, Nitrogen and carbon dioxide atmospheres and so on, of which the Nitrogen atmosphere is preferred. Said inert atmosphere may be an inert atmosphere in flowing state, or in static state. Preferably, said inert atmosphere is one in static state, i.e. the heating treatment of the impregnated catalyst with the sulfurized olefin-containing product is carried out in said inert atmosphere under closed condition. Said inert atmosphere may be at an atmospheric pressure, or a pressure lower or higher than the atmospheric pressure, but preferably the atmospheric pressure or a pressure higher than the atmospheric pressure, more preferably the process is carried out under 0.1xcx9c5 MPa.
Said heating temperature for treating the catalyst in an inert atmosphere is preferably 150xcx9c300xc2x0 C. while the treatment time is preferably for 2xcx9c5 hours.
According to the method of the present invention, the catalyst obtained by the presulfurization of the catalyst should be activated prior to use to convert the metal oxides active for hydrogenation in the catalyst into sulfurization state. The conventional method may be used for activation of the catalyst, i.e. the catalyst is contacted with hydrogen at a temperature higher than 200xc2x0 C., preferably 200xcx9c425xc2x0 C., for at least 0.5 hour, preferably 0.5 hourxcx9c3 days. The activation method of the catalyst may also be carried out in the presence of hydrogen by heating gradually the catalyst to a temperature required for reactions of hydrodesulfurization, hydrodenitrogenation or hydrocracking, generally at a temperature between 200xc2x0 C. and 450xc2x0 C.
Compared with the prior art, the presulfurization method of hydrogenation catalysts according to the present invention has the advantages as follows:
(1) After being treated in an inert atmosphere at the same temperature, the sulfurized catalyst provided according to the present invention can be maintained at a higher level of sulfur retention compared with the catalyst of the prior art. Furthermore, if it is desired to achieve the same level of sulfur retention, the treatment temperature required in the method according to the present invention is lower than that of the prior art.
For example, after a hydrotreating catalyst containing oxides of nickel and tungsten was presulfurized according to the method of the present invention, it was finally treated in an inert atmosphere at 205xc2x0 C. for 3 hours to obtain a catalyst having a sulfur content of 4.22 wt %, then sulfur in the resultant catalyst was extracted with acetone under refluxing condition for 18 hours, the extracted catalyst had a sulfur level of 3.74 wt % and a sulfur retention degree of 88.6 wt %. However, as disclosed in U.S. Pat. No. 5,215,954, when the same olefin-containing components were used for the presulfurization of catalyst in the inert atmosphere at the same temperature for the same period of time, and the same method was used to carry out the acetone extraction test of the catalyst, the sulfur contents in the catalyst before and after extraction were reduced from 3.25 wt % to 2.00 wt %, and the sulfur retention degree with acetone extraction was only 61.5 wt %.
Also, for example, after a catalyst was presulfurized according to the method of the present invention, it was finally treated in an inert atmosphere at a temperature of 190xc2x0 C. to obtain, a presulfurized catalyst having a sulfur content of 5.97 wt %, then the acetone extraction test was carried out by the same method, the extracted catalyst had a sulfur content of 3.70 wt % and its sulfur retention degree was 62 wt %. These results were similar to that (60.5 wt %) by the method disclosed in U.S. Pat. No. 5,215,954 in which the treatment temperature in an inert atmosphere was at 205xc2x0 C.
Further, for example, decene (containing 98 wt % of xcex1-C10 olefin), powdered elemental sulfur and powder promoter of tetramethylthiuram disulfide were first reacted by the method according to the present invention, then the catalyst containing elemental sulfur was impregnated with the sulfurized olefin-containing product formed in the reaction, and heat-treated to obtain a presulfurized catalyst. Thereafter, the same acetone extraction test of the obtained catalyst was carried out, the sulfur contents of the catalyst before and after the extraction were respectively 5.61 wt % and 5.45 wt %, and the sulfur retention degree was 97.1 wt %. But in contrast, according to the results shown in Table 2 disclosed in U.S. Pat. No. 5,215,954, in which no promoter was added and similar olefin was used directly to treat the catalyst according to the method of U.S. Pat. No. 5,215,954, the sulfur retention degree was only 92.2 wt %.
(2) The raw materials used by the method according to the present invention are cheap elemental sulfur, olefin and a small amount of promoter, and the promoter used was in a quantity much less than that used in the prior art, therefore, the cost for the presulfurization process has been reduced remarkably while the sulfur retention degree is improved significantly.
(3) The catalyst presulfurized according to the method of the present invention has relative high catalytic activity. For example, having been presulfurized by the method according to the present invention, the hydrotreating catalyst has the hydrodesulfurization and hydrodenitrogenation activities similar to that of the presulfurized catalysts obtained by the in-situ method of presulfurization.